TY - GEN

T1 - How many bits of feedback is multiuser diversity worth in MIMO downlink?

AU - Diaz, Jordi

AU - Simeone, Osvaldo

AU - Bar-Ness, Yeheskel

PY - 2006

Y1 - 2006

N2 - The impact of multiuser diversity on MIMO down-link is generally measured in terms of two asymptotic quantities derived from the sum-rate, namely the scaling law of the sum-rate versus the number of users n (for a fixed signal-to-noise ratio, SNR) and the multiplexing gain (i.e., asymptotic growth of the sum-rate versus SNR). Designing optimal strategies with respect to these two criteria requires the availability of Channel State Information (CSI) at the transmitter, which in turn demands feedback of information from receivers to the transmitter. An open question is: how many bits of feedback are really necessary to achieve optimality of these criteria, i.e., to fully exploit multiuser diversity? In this paper, the optimal scaling law of the sum-rate with respect to n, for fixed SNR, fixed number of transmit antennas M and any number of receiving antennas N (i.e., M log log nN), is proved to be achievable with a deterministic feedback of only one bit per user. The impact of adding feedback bits is also investigated. Furthermore, it is shown that the optimal multiplexing gain of M is guaranteed if the total feedback per cell is proportional to the SNR (in dB). The proofs build on opportunistic beamforming and binary quantization of the signal-to-noise-plus-interference ratio.

AB - The impact of multiuser diversity on MIMO down-link is generally measured in terms of two asymptotic quantities derived from the sum-rate, namely the scaling law of the sum-rate versus the number of users n (for a fixed signal-to-noise ratio, SNR) and the multiplexing gain (i.e., asymptotic growth of the sum-rate versus SNR). Designing optimal strategies with respect to these two criteria requires the availability of Channel State Information (CSI) at the transmitter, which in turn demands feedback of information from receivers to the transmitter. An open question is: how many bits of feedback are really necessary to achieve optimality of these criteria, i.e., to fully exploit multiuser diversity? In this paper, the optimal scaling law of the sum-rate with respect to n, for fixed SNR, fixed number of transmit antennas M and any number of receiving antennas N (i.e., M log log nN), is proved to be achievable with a deterministic feedback of only one bit per user. The impact of adding feedback bits is also investigated. Furthermore, it is shown that the optimal multiplexing gain of M is guaranteed if the total feedback per cell is proportional to the SNR (in dB). The proofs build on opportunistic beamforming and binary quantization of the signal-to-noise-plus-interference ratio.

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U2 - 10.1109/ISSSTA.2006.311822

DO - 10.1109/ISSSTA.2006.311822

M3 - Conference contribution

AN - SCOPUS:46149085436

SN - 0780397800

SN - 9780780397804

T3 - IEEE International Symposium on Spread Spectrum Techniques and Applications

SP - 505

EP - 509

BT - ISSSTA-06 - 2006 IEEE 9th International Symposium on Spread Spectrum Symposium on Spread Spectrum Techniques and Applications, Proceedings

T2 - ISSSTA-06 - 2006 IEEE 9th International Symposium on Spread Spectrum Symposium on Spread Spectrum Techniques and Applications

Y2 - 28 August 2006 through 31 August 2006

ER -